lumirb

yes, it was the lang-switcher plugin on my system as well!

Now it works. You need the version 1.20 of the plugin.

I had the same problem…

If you take a look at the end of the file wp-comments-post.php, you can see the row:

$location = (empty($_POST[‘redirect_to’])) ? $_SERVER[“HTTP_REFERER”] : $_POST[‘redirect_to’];

I had a problem with the variable HTTP_REFERER.

There could be two problems:
1. internet browser
2. others

More details:
https://codex.www.ads-software.com/Enable_Sending_Referrers

I had a problem with my subdomain. It works now!:-)